Centrifugal fans



y 1950 J. c. BUSQUET 2,938,660

CENTRIFUGAL FANS Filed March 17, 1958 yew/70 United States Patent ce CENTRIFUGAL FANS Jan C. Busquet, Hengelo, Netherlands, assignor to Koninklijke Machinefahriek Gehr. Stork & Co. N.V., Hengelo, Netherlands Filed Mar. 17, 1958, Ser. No. 721,750

Claims. (Cl. 230-128) This invention relates to a centrifugal fan having an impeller, in which the fluid enters at both sides, said impeller being provided with hollow blades having one or more discharge openings for a pressure fluid entering the interior of the blades.

The invention has for its object to provide a centrifugal fan of this kind in which the inflow of the impeller is not obstructed by means for introducing the pressure fluid into the hollow impeller blades.

According to the invention the impeller blades are divided in radial direction and the blade parts extend between the side walls of the impeller and two partitions substantially parallel to said side Walls, said partitions constituting the side walls of a chamber, closed at its circumference and communicating with the cavities in the blades and a pressure fluid being introduced into said chamber. With a preferred embodiment of the centrifugal fan according to the invention the impeller itself may generate the required pressure of the fluid to be introduced into the hollow blades by means of auxiliary blades arranged on the opposite sides of the partitions of the impeller and extending between one of said partitions and a plate substantially parallel thereto, said auxiliary blades being enclosed at their outer ends by an annular wall and the partitions being provided with apertures at the impeller blades.

The invention will be further described with reference to the accompanying drawing which illustrates an embodiment of a fan according to the invention.

In the drawing Fig. 1 shows a longitudinal section of a centrifugal fan taken on the line II of Fig. 2 which itself is a cross-sectional view of the fan.

Fig. 3 is a cross-section of a flat tube of modified construction between the chamber in the impeller and the circumferential wall of the casing.

The impeller 1 is secured to shaft 2 and on both sides has an inflow opening adjoined to the inflow mouth 3 and 4 of the casing 5 respectively.

Hollow blade parts extend between the side wall 6 of the impeller and a radial partition 8 and hollow blade parts 10 also extend between the side wall 7 and a radial partition 9 of the impeller. The blades 10 at their rear end are provided with a discharge opening 11 which may extend as a slot on the whole width of the blade.

Secured to the opposite sides of the partitions 8 and 9 are auxiliary blades 12, which at their other side are secured to a plate 13 and 14 respectively so that said plates also form part of the impeller. The outer ends of the auxiliary blades 12 are enclosed by a circumferential wall 15 arranged between the impeller plates 8, 13 and 9, 14 respectively. The chamber 16 constituted by the plates 13 and 14 is closed at its circumference by a stationary plate 17, which by means of resilient strips 18 is sealed with respect to the impeller body.

A flat tubular body 19 is connected to the chamber 16 and has a more or less streamlined section as indicated in dotted lines in Fig. 2. The tubular body 19 extends between the stationary circumferential Wall 17 of the impeller and the circumferential wall 20 of the fan casing. The part 21 of the wall 20 is hinged and constitutes a valve provided with a shaft or pivot 22. At the outer side of the casing a handle 28 is secured to the shaft 22 for adjusting valve 21. If the valve 21 is adjusted to its dotted line position in Fig. 2, part of the fluid discharged from the impeller into the surrounding casing flows through the guide vanes 23 into the tubular body 19 and from there into the chamber 16, so that the fluid is drawn in by the auxiliary blades 12 according to the arrows shown in Fig. 1 and flows through the apertures 24 of the plate 8 or 9 respectively into the impeller blades 10 in order to be discharged through the openings 11 at the rear end of the blades. The quantity of fluid flowing out of the blades may be varied by adjusting the plate 21.

As according to the embodiment shown in Figs. 1 and 2 the fluid is introduced into the tubular body 19 at its outer end, the circumferential wall 20 of the fan casing should be provided with an entension 25. Said extension, however, may be omitted by shaping the front wall of the body 19 as a hinged valve or valves 26, each of which have a pivot axis 27, as shown in Fig. 3. The valves 26 may be adjusted from the outside of the casing and to this end a toothed sector 29 is secured to each pivot axis 27. Said sectors 29 mesh with each other and one of said axis 27 is provided with a handwheel 30 for rotating the valve 26.

What I claim is:

l. A centrifugal fan comprising a casing including a circumferentially extending wall having an opening defining an outlet and side walls at least one of which has an opening defining an intake, an impeller rotatably mounted in said casing, a pair of radially extending partitions on said impeller, a stationary cylindrical wall in said casing surrounding the portion of said impeller between said pair of partitions and cooperating therewith to define a chamber, hollow blades on said impeller and operable to draw fluid through said intake and expel such fluid through said outlet, the interiors of said blades being in communication with said chamber and having trailing edges with discharge openings therein, a tubular body extending between said stationary cylindrical wall and a wall of said casing and in communication with said chamber, and means connected with said tubular body for introducing fluid into said body for passage through said chamber and the interior of the blades to be discharged under pressure through said discharge opem'ngs to influence the fluid flow over said trailing edges.

2. A centrifugal fan according to claim 1 wherein said fluid introducing means includes a part of the circumferentially extending wall of the fan casing which is located adjacent an upstream portion of the tubular body with respect to the direction of fluid flow, said tubular body having an entry opening in the wall thereof communicating with the interior of the tubular body to communicate said casing with said chamber, and said fluid introducing means also including a hinged valve adapted Patented May 31, 1960 perpendiculart'o the impeller' axis. j r

is of elongated-sectiom having its longer sides in planes l0 Q 7 centrifngal fan as claimed in claim l, characterized in that the tubular body extending between the stationary wall of the chamber and a wall of the fan casing at its upstream face is provided with at least one hinged valve.

References Cited in the file of this patent FOREIGN PATENTS 758,906 Great Britain L Oct. 10, 1956 

